Grand Prix fans are being warned not to attend the Silverstone race track as heavy rain on Friday left thousands stranded in traffic jams near the site.
The deluge affected race fans outside the Northamptonshire track and left some car parks unusable.
Silverstone managing director Richard Phillips last night issued an "unreserved apology" to fans, adding the incident almost reduced him to tears.
Mr Phillips said the financial hit is likely to run into seven figures, which for this season will potentially turn a profit into a loss.
He said organisers were in emergency meetings every two hours on Friday with the police, highways agencies, county council, emergency planning to "try and resolve the issues".
He added: "It's going to cost us a lot of money. I honestly don't know the figure, but it could be a lot more than hundreds of thousands (of pounds). For people who did not get in we're offering refunds, and for anybody who doesn't get in we'll be offering refunds as well.
"Right now we're trying to get ourselves into a situation to get in as many people as we can from a position of devastation. But I unreservedly apologise to people. I feel very responsible for it, this is something I've been very proud of over the years and I almost could cry now."
Problems started when a deluge of up to 40 millimetres of rainfall fell in a 12-hour period. By mid-afternoon all campsites in and around Silverstone had to be closed.
With camping grounds sodden, caravans and motorhomes had to be escorted in one at a time when ordinarily they would have driven straight in, backing up the traffic. It is the loss of the car parks that caused major headaches for all concerned as they hope for them to dry out to re-use them on Sunday.
Even F1 supremo Bernie Ecclestone was contacted and told not to bother turning up. Phillips said: "We dissuaded him from coming in. He was coming in by road, but he could have been five hours, I guess."